1. Field of the Invention
The present invention relates to a manufacturing method for electronic devices with which uniform application of photosensitive or non-photosensitive resin such as resist onto a substrate is enabled during manufacturing processes of electronic devices such as liquid crystal display devices employing semiconductor devices.
2. Discussion of the Background
An explanation will be given based on a case in which patterns for liquid crystal display elements employing TFT (thin film transistor) are formed by utilizing a stepper exposure device. A photo-resist having photosensitive characteristics is uniformly applied onto a glass substrate on which there is formed a metal thin film or dielectric thin film. Onto this substrate, patterns formed as masks are subsequently treated by projecting and exposing by a stepper, and patterns for display elements are exposed and transferred onto the photo-resist. The exposed and transferred patterns further undergo developing, etching and resist exfoliating. By repeating the same processes several times, a wiring pattern, an insulating film pattern, and a semiconductor layer pattern are laminated to form display elements. Such a conventional art is also disclosed in the column of "Prior Art" of Japanese Unexamined Patent Publication No. 305651/1992. The resist application process is also disclosed in "The Sixth Fine Process Technologer/Japan '96 Seminar Resume: Manufacturing Device Course (R6) Latest Tendencies in Photo-processing Technology", Pages 3 to 21. FIGS. 7 and 8 are diagrams showing a series of processes of film forming, resist applying, exposing, developing, etching and resist exfoliating. In the drawings, 100 denotes a substrate, 101 a thin film such as metal film or insulating film formed on the substrate, 102 photosensitive resin such as resist, 103 a mask, and 104 a pattern portion of the mask 103, respectively. FIG. 9 is a diagram showing application processes through central dropping and rotation (uniformization) of resin which is one method for the resin application process. In the drawings, 110 denotes a substrate, 111 a nozzle for dropping resin, and 112 photosensitive or non-photosensitive resin such as resist, respectively. FIG. 10 is a diagram showing application processes, i.e. slit nozzle dropping, completion of dropping, and rotation (uniformization) of resin which is another method for the resist application process. In the drawings, 120 denotes a substrate, 121 a slit-type nozzle for dropping resin, and 122 photosensitive or non-photosensitive resin such as resist, respectively.
The prior art process will now be explained. As shown in FIG. 7, the thin film 101 such as metal film or insulating film is formed onto the substrate 100 by using a CVD device or spattering device (FIG. 7(b)). Then, the photosensitive resin 102 such as positive resist is applied onto the substrate 100 by rotational application (FIG. 7(c)). Exposing of the substrate 100 applied with resist is performed by employing, for example, a stepper. At this time, the shutter of the stepper is released for several seconds until an appropriate light exposure for the resist is reached for the exposure, the resist is exposed, and the pattern is transferred onto the substrate 100 as a resist photosensitive image (FIG. 7(d)). After completion of exposing, the substrate 100 is treated with a developer for developing and the photosensitive image of the transferred mask pattern is formed on the substrate 100 as a resist image, as shown in FIG. 8(a). Then, etching of the formed thin film 101 is performed (FIG. 8(b)), and the resist 102 is exfoliated thereafter (FIG. 8(c)). By repeating these processes several times, a wiring pattern, an insulating film pattern and a semiconductor layer pattern are laminated to form display elements.
A prior art resist application method will now be explained. The central dropping method which is a general resist application method will be explained. As shown in FIG. 9, photosensitive or non-photosensitive resin 112 such as resist is dropped by a specified amount through the nozzle 111 from centrally above the substrate 110, and after the resin has naturally spread after a specified time has elapsed, the substrate is rotated to make the resin spread uniformly over the whole substrate in order to perform application. Another resist application method, i.e. the slit dropping method will be explained. As shown in FIG. 10, photosensitive or non-photosensitive resin 122 such as resist is dropped and applied uniformly and over the whole substrate by making the slit nozzle 121 scan along the substrate 120 in a parallel manner, and the substrate is rotated thereafter to further improve the uniformity of the applied film thickness. If the targeted uniformity of film thickness can be obtained by the slit application alone, the following rotating process might be omitted.
According to prior art manufacturing methods, in the case where resin is applied by employing the central dropping method, resin needs to be dropped onto the substrate in an amount that is sufficient for self-spreading and spreading over the whole substrate by the following rotating process, and the ratio of the amount of resin finally applied onto the substrate to that of initially dropped resin will reach approximately 1:97 to 99, thereby presenting a drawback that the efficiency of effective usage is low. On the other hand, in the case where resin is to be applied by the slit dropping method, the amount of resin to be dropped onto the substrate will be approximately 1/10 to 1/3 of that of the central dropping method. However, when the amount of droppings is decreased or clogging due to foreign matters or hardened resin in the slit nozzle has occurred, there might be generated broken portions 133 (irregular (shortage) regions of droppings) of the resin 132 in the scanning direction as shown in FIGS. 11(a) and (b) in applying photosensitive or non-photosensitive resin 132 such as resist by scanning the slit-like nozzle 131 over the substrate 130. Especially in cases in which such broken portions are generated at a central portion (center of rotation) of the substrate, extending substantially in a radial manner from the center of the substrate in directions of the centrifugal force, inertial force and frictional force (between substrate and resin), it became difficult to ensure uniformity of applied film thickness by the following rotation of the substrate, depending on the amount (degree) of shortage of the droppings.
When photosensitive resin is employed and the applied film thickness becomes irregular, excess/shortage of appropriate exposing energy occurs between the irregular portions and peripheral normal portions, which might lead to pattern defects. In case non-photosensitive resin is employed, irregularities in required characteristics such as irregularities in capacitance formed by the film thickness or irregularities in transmittance, which are objects of the film itself have occurred, and thus caused inconveniences to result in deficiencies.
It is an object of the present invention to provide a manufacturing method for electron devices with which a desired film thickness of favorable uniformity can be secured, generation of pattern defects be decreased, and stable quality be obtained.